• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.167-175
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• 2000

Compressed bitstreams generated by an MPEG-2 video encoder (or digital TV picture transmission are quite sensitive to channel errors. Due to the coding structure of the MPEG-2 video compression algorithm, a single bit error can affect not only the current Picture frame but also succeeding frames. Error concealment algorithms attempt to repair damaged portions of the picture by exploiting spatial and temporal redundancies in the correctly received and reconstructed video frames. In this paper, we analyze the effect of channel errors in MPEG-2 video bitstreams and estimate lost motion vectors by exploiting temporal redundancies in the video frames. Motion vectors can be estimated from the vertically adjacent extended region of lost macroblocks. Finally, we conceal the damaged macroblocks by compensating the displacement with the estimated motion vectors. Simulation results demonstrate that both the weighted sum algorithm and the extension matching algorithm achieve good performance in terms of PSNR values as well as subjective image quality.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4780-4785
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• 2012

As many mobile devices such as smart phones and tablets are widely spread, optimized mobile video encoder used during video recording application is needed. In this paper, we implemented H.264/AVC base profile video encoder on a mobile device and empirically optimized control parameters of the encoder. As the experiment, we more than 100 test cases were designed with varying Lagrangian optimization, Hadamard Transform, search range, I-frame period, and reference frames. During the experiment, we measured picture quality, bit-rate, encoding time, motion estimation time, and power consumption. From the result, we can determine optimal values for the H.264 control parameters.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.245-247
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• 1999

본 논문은 MPEG-2 TM 5 비디오 부호기의 움직임 예측(motion estimation) 처리과정을 소개한다. 비디오에는 공간의 중복성보다 시간의 중복성이 훨씬 많다. 따라서 시간의 중복성을 찾아내는 것이 압축의 효율을 높이는 중요한 척도가 된다. MPEG-2 부호기는 움직임 예측 알고리즘을 사용하여 시간의 중복성을 줄여 압축 효율을 높인다. 움직임 예측은 참조 블록의 위치로부터 원래 블록의 위치를 추정하여 최적의 움직임 벡터를 찾는 과정이다. PMEG-2에서의 움직임 예측은 full search 알고리즘을 사용하여 마지막으로 hlaf pel로 산출한다. 본 논문에서는 MPEG-2 움직임 예측 과정을 frame estimation, field estimation, picture 타입에 따른 estimation, 움직임 예측을 위한 블록 매칭 알고리즘, full search 방법 및 움직임 벡터에 대하여 소개한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2372-2382
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• 1998

In this paper, we propose a new edge based finite state vector quantization method having better performance than conventional side-match finite state vector quantization. In our proposed scheme, each dCT transformed block is classified to 17 classes according to edge types. Each class has a different codebook based on its characteristis. Encoder classified each block to motion block or stationary block and constructed a merging map by using edge and motion information, and sent to decoder. We controled amoutn of bing bits transmitted with selecting modes accoridng to bandwidth of transmitting channel. Compared with conventional algorithms, H.263 and H.261 at low bit rate, our proposed algorithm shows better picture quality and good performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.397-400
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• 2016

In this paper, we propose an efficient algorithm for computing architecture for high-performance Inter Prediction SAD HEVC encoder. HEVC Motion Estimation (ME) of the Inter Prediction is a process for searching for the currently high prediction block PU and the correlation in the interpolated reference picture in order to remove temporal redundancy. ME algorithm uses full search(FS) or fast search algorithm. Full search technique has the guaranteed optimal results but has many disadvantages which include high calculation and operational time due to the motion prediction with respect to all candidate blocks in a given search area. Therefore, this paper proposes a new algorithm which reduces the computational complexity by reusing the SAD operation in full search to reduce the amount of calculation and computational time of the Inter Prediction. The proposed algorithm is applied to an HEVC standard software HM16.12. There was an improved operational time of 61% compared to the traditional full search algorithm, BDBitrate was decreased by 11.81% and BDPSNR increased by about 0.5%.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1029-1039
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• 2012

In this papar, we propose a new motion estimation and coding technique using adaptive motion vector resolution. Currently, HEVC encodes a video using 1/4 motion vector resolution. If there are high texture regions in a picture, HEVC can't get a performance enough. So, we insert additional 1-bit flag meaning whether motion vector resolution is 1/4 or 1/8 in PU syntax. Therefore, decoder can recognize the transmitted motion vector resolution. Experimental results show that maximum coding efficiency gain of the proposed method is up to 5.3% in luminance and 7.9% in chrominance. Average computional time complexity is increased about 33% in encoder and up to 5% in decoder.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.259-261
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• 1999

본 논문은 MPEG-2 TM 5 video 부호기의 전체구조 및 처리과정을 기술한다. MPEG-2는 저장 매체, 통신, 방송 매체 등을 위한 동영상 압축이 표준이다. MPEG-2 압축 방법에는 공간적 압축과 시간적 압축 방법이 있다. 공간적 압축 방법에는 화면에서의 중복성을 줄이기 위한 표본화 주파수(4:4:4, 4:2:2, 4:2:0, format), DCT, scanning(zigzag 혹은 alternate scanning)과 quantization이 있고 시간적 압축 방법에는 움직임 예측(motion estimation)과 I, P, B-picture를 사용하는 방법이 있다. 본 논문에서는 MPEG-2 부호기의 핵심을 전체 구조, DPCM, MPEG bitstream syntax, MPEG-2 부호화 알고리즘, 움직임 예측, 움직임 벡터, rate control 그리고 가변길이 코딩(variable length coding)으로 구분하여 소개한다.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.99-106
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• 2005

In recent years, vision sensors are widely used to mobile robot for navigation or exploration. The analog signal transmission of visual data being used in this area, however, has some disadvantages including noise weakness in view of the data storage. A large amount of data also makes it difficult to use this method for a mobile robot. In this paper, a digital data compressing technology based on MPEG4 which substitutes for analog technology is proposed to overcome the disadvantages by using DWT(Discreate Wavelet Transform) instead of DCT(Discreate Cosine Transform). The TI Company's DSP chip, TMS320C6711, is used for the image encoder, and the performance of the proposed method is evaluated by PSNR(Peake Signal to Noise Rates), QP(Quantization Parameter) and bitrate.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.138-145
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• 1997

This paper proposes an adaptive algorithm for the quantization step size control of MPEG-2, using the information obtained from the previously encoded picture. Before quantizing the DCT coefficients, the properties of reconstruction error of each macro block (MB) is predicted from the previous frame. For the prediction of the error of current MB, a block with the size of MB in the previous frame are chosen by use of the motion vector. Since the original and reconstructed images of the previous frame are available in the encoder, we can calculate the reconstruction error of this block. This error is considered as the expected error of the current MB if it is quantized with the same step size and bit rate. Comparing the error of the MB with the average of overall MBs, if it is larger than the average, small step size is given for this MB, and vice versa. As a result, the error distribution of the MB is more concentrated to the average, giving low variance and improved image quality. Especially for the low bit application, the proposed algorithm gives much smaller error variance and higher PSNR compared to TM5 (test model 5).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.842-847
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• 2004

We present a new video coding technique to tradeoff frame rate and picture quality for low bit rate video coding. We show a model equation for selecting the optimal frame rate from the motion content of the source video. We can determine DCT quantization parameter (QP) using the frame rate and bit rate. For objective video quality measurement we propose a simple and effective error measure for skipped frames. The proposed method enhances the video quality up to 2 ㏈ over the H.263 TMN5 encoder.